Microacoustic components comprise a functional region in which acoustic waves are capable of propagation. Such components can include, e.g., electroacoustic transducers comprising electrode structures and a piezoelectric material and operate with SAWs (SAW=surface acoustic wave), with BAWs (BAW=bulk acoustic wave) or with GBAWs (GBAW=guided bulk acoustic wave). Such components can constitute RF filters and be used, e.g., in mobile communication devices.
A characteristic order of sizes of RF filters operating with acoustic waves is substantially provided by the velocity of propagation of acoustic waves in condensed matter and the frequency. At a frequency of 1 GHz and a velocity of propagation of 1000 m/s, a characteristic order of size of 1 μm results. In this regard, for example, adjacent electrode fingers of SAW components or piezoelectric layer thicknesses of BAW resonators are determined by structure sizes of the order of size of 1 μm.
What is problematic about microacoustic components, in principle, is that the functional regions react sensitively to external influences. Therefore, covers are required above the functional regions. However, conventional covers make the production costs more expensive and/or are at odds with the continuous trend towards miniaturization.
What is furthermore problematic about microacoustic components is that complex technical measures for providing an optimum medium for acoustic signals are necessary if stringent requirements are made of the signal quality. In this regard, e.g., one measure for SAW components consists in optimally setting the waveguide properties for different regions of an acoustic track. In this case, the propagation of an acoustic wave, e.g., in a piezoelectric material or at the surface of a piezoelectric material, is dependent on a multiplicity of parameters, such as e.g., the density, the mass per unit area of the medium, the modulus of the elasticity of the medium or the geometry of the functional region, that is to say of the region in which the wave propagates.